Abstract The partition equilibrium was investigated in relation to the steam-blowing and stripping, during and after the hydroperoxidation of cumene, and the following results were obtained. 1. Equilibrium constant K does not depend on the concentration of CHP within the limit of experimental error, but it depends on the temperature. 2. The partition constant, K approximately satisfies the following formula, K=1.3_4×10^-4e^1580/T. 3. The heat of transference of 1 mol. of cumene hydroperoxide from cumene solution into water under the equilibrium condition, was determined as 3.16 k cal./mol.